1. Field of the Invention
The present invention relates to a sheet-through type image reader which, while transporting a read-target document so as to move on one side of a main surface of a transparent plate, reads the image of the document from the other side of the main surface of the transparent plate, and an image forming device having this image reader.
2. Description of the Related Art
When an image of a document is read using a sheet-through type image reader and printed by a printer, or loaded to a computer, such as a personal computer, and is displayed on a screen, a striped image along the sub-scanning direction may appear in the image. This is normally caused by foreign substances, such as dirt, dust or paper dust from the document being transported, or by a scratch on the glass. The striped image appears as a black strip on the white background portion, or as a white strip on the image portion, and visually stands out, therefore removal of such a striped image is desired for an image reader which is demanded to create an image faithful to the document.
An example of a technology aiming at suppressing the generation of this striped image is disclosed in Japanese Patent Application Laid-Open No. H10-294870, where if a pixel position is specified as a pixel of a dirt component, an image correction unit 10 applies a pixel matrix in which the pixel position is a target pixel RT, extracts pixels which are not specified as a pixel of the dirt component (that is, pixels with a normal value) included in the pixel matrix, calculates an average value of the pixels with a normal value, and outputs the calculated average value as a digital image signal DAc after correcting the target pixel RT.